As effects of catechins, there have been reported an inhibitory effect on α-amylase activity and the like (see, for example, JP-A-03-133928). To such a physiological effect to manifest, it is necessary for an adult to drink tea as much as 4 to 5 cups in a day. Accordingly, there has been a demand for a technology that enables the addition of catechins at high concentration in beverages to facilitate the ingestion of a large amount of catechins. As one of methods for this, catechins are added in a dissolved form to a beverage by using a green tea extract (see, for example, JP-A-59-219384).
Packaged beverages of green tea are accompanied by the problem of dregs caused by high molecular components such as pectin and hemicellulose during long-term storage, and a variety of methods have been reported for its resolution, including the use of an ultrafiltration membrane (see, for example, JP-A-4-45744).
Treatment methods using various adsorbents, without using any ultrafiltration membrane, have also been attempted (see, for example, JP-A-62-278948 and JP-A-57-29250)
Concerning the technology on the application of zeolite to tea leaves, on the other hand, the addition of zeolite to green tea leaves or to a substance derived from green tea leaves has been studied (see, for example, Published Japanese Translation No. 2000-508916 of PCT International Application).